Method of making multilayer polyurethane protective film

ABSTRACT

A method of making a multilayer protective film. The method comprises: (a) forming a PU layer comprising an at least partially crosslinked polyurethane, the at least partially crosslinked polyurethane comprising at least one of a polyester-based polyurethane or a polycarbonate-based polyurethane; (b) forming a TPU layer comprising a polycaprolactone-based thermoplastic polyurethane; (c) forming a PSA layer comprising a pressure sensitive adhesive; (d) bonding one major surface of the PU layer to one major surface of the TPU layer; and (e) bonding the PSA layer to an opposite major surface of the TPU layer; wherein the TPU layer is sandwiched between the PU layer and the PSA layer. The multilayer film may be used to protect painted surfaces of vehicle body parts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371International Application No. PCT/US2007/080146, filed Oct. 2, 2007,which claims priority to U.S. Provisional Application Ser. No.60/828,106, filed Oct. 4, 2006.

BACKGROUND

Multilayer films that include one or more layers of a polyurethanematerial are known. Some of these films are disclosed in U.S. Pat. No.6,607,831 (Ho); U.S. Pat. No. 5,405,675 (Sawka et al); U.S. Pat. No.5,468,532 (Ho et al); U.S. Pat. No. 6,383,644 (Fuchs); as well as PCTInternat. Publ. No. WO 93/24551 A1 (Pears et al.). Some of these filmshave been used in surface protection applications. For example, actualfilm products that have been used to protect the painted surface ofselected automobile body parts include multilayer films manufactured foryears by 3M Company, St. Paul, Minn., under the trade designationsSCOTCHCAL high performance protective film PUL0612, PUL1212 andPUL1212DC. Each of these 3M Company film products includes athermoplastic polyester-based polyurethane layer that is backed by apressure sensitive adhesive (PSA) on one major surface and covered by awater-based polyester-based or polycarbonate-based polyurethane layer onthe opposite major surface.

SUMMARY

In one aspect, the present invention provides a method of making amultilayer protective film, the method comprising steps:

(a) forming a PU layer comprising an at least partially crosslinkedpolyurethane, the at least partially crosslinked polyurethane comprisingat least one of a polyester-based polyurethane or a polycarbonate-basedpolyurethane;

(b) forming a TPU layer comprising a polycaprolactone-basedthermoplastic polyurethane;

(c) forming a PSA layer comprising a pressure sensitive adhesive;

(d) bonding one major surface of the PU layer to one major surface ofthe TPU layer; and

(e) bonding the PSA layer to an opposite major surface of the TPU layer;wherein the TPU layer is sandwiched between the PU layer and the PSAlayer, and wherein

at least one of steps (a) or (b) comprises step:

-   -   (i) forming a rolling bank of a polyurethane precursor material        comprising at least one polyisocyanate and at least one polyol,        wherein the rolling bank contacts first and second substrates;        -   passing the first and second substrates with the            polyurethane precursor material disposed therebetween            through a nip;        -   heating the polyurethane precursor material under conditions            such that it forms the PU layer or the TPU layer in contact            with the first and second substrates; and        -   optionally removing at least one of the first or second            substrates from the PU layer or the TPU layer to expose an            outer surface of the PU layer or the TPU layer,            respectively; or

step (b) comprises step:

-   -   (ii) introducing components comprising a diisocyanate and a diol        into an extruder to provide a molten thermoplastic polyurethane;        -   extruding the molten thermoplastic polyurethane through a            die onto a third substrate;        -   passing at least the third substrate and the extruded molten            thermoplastic polyurethane through a nip to provide a layer            of thermoplastic polyurethane on the third substrate; and        -   solidifying the thermoplastic polyurethane; or

step (a) comprises step (i) and step (b) comprises step (ii).

In some embodiments, steps (a) to (e) are carried out sequentiallyand/or consecutively.

In some embodiments, said multilayer protective film is transparentand/or colored. In some embodiments, the method further comprises sizingand shaping the multilayer protective film to conform to a surface of avehicle body part.

In some embodiments, step (a) further comprises: coating anaqueous-based polyurethane dispersion onto a releasable carrier. In someembodiments, step (a) further comprises: coating a solvent-basedpolyurethane solution onto a releasable carrier.

In some embodiments, step (b) comprises: extruding thepolycaprolactone-based thermoplastic polyurethane at an elevatedtemperature through a die to form the TPU layer.

In some embodiments, at least one of steps (a) or (b) comprises step(i). In some embodiments, step (b) comprises step (ii).

In some embodiments, step (d) comprises: laminating the one majorsurface of the PU layer to the one major surface of the TPU layer whilethe one major surface of the TPU layer is at an elevated temperaturethat is sufficiently higher than room temperature to facilitate adequatebonding between the PU layer and the TPU layer.

In some embodiments, step (d) comprises: laminating one major surface ofthe PU layer to one major surface of the TPU layer after said extrudingand with at least the one major surface of the PU layer and the TPUlayer being at a temperature that is too low to facilitate adequatebonding between the PU layer and the TPU layer; and heating the onemajor surface of the TPU layer to an elevated temperature that issufficiently higher than room temperature to facilitate adequate bondingbetween the PU layer and the TPU layer during said laminating, whereinsaid heating occurs before or during said laminating.

In some embodiments, the method further comprises corona treating theopposite major surface of the TPU layer. In some of these embodiments,the method further comprises: releasably laminating an opposite majorsurface of the TPU layer to a releasable carrier web after saidextruding. In some of these embodiments, the method further comprises:exposing the opposite major surface of the TPU layer, after saidreleasably laminating; and corona treating the opposite major surface ofthe TPU layer, after said exposing and before said bonding the PSAlayer.

In some embodiments, said at least partially crosslinked polyurethane isthe reaction product of a polyol and at least a diisocyanate, and saidpolyol is a polyester polyol, a polycarbonate polyol or a combination ofboth. In some of these embodiments, said polyol is an aliphatic polyol.In some of these embodiments, said at least one polyisocyanate comprisesa diisocyanate and a triisocyanate. In some of these embodiments, saidtriisocyanate is an aliphatic triisocyanate. In some of theseembodiments, the said diisocyanate is an aliphatic diisocyanate (forexample, isophorone diisocyanate and/orbis(4-isocyanatocyclohexyl)methane). In some embodiments, said at leastpartially crosslinked polyurethane comprises said polycarbonate-basedpolyurethane and/or said polyester-based polyurethane.

In some embodiments, said at least partially crosslinked polyurethane isa combination of said polyester-based polyurethane and saidpolycarbonate-based polyurethane. In some embodiments, said polyurethaneis an aliphatic polyurethane. In some embodiments, said at leastpartially crosslinked polyurethane is a slightly crosslinkedpolyurethane. In some embodiments, said at least partially crosslinkedpolyurethane comprises a water-based polyurethane and/or a solvent-basedpolyurethane.

In some embodiments, said PU layer has an exposed major surface with theappearance of having been cast onto a smooth major surface of areleasable carrier web, dried and the carrier web removed. In someembodiments, the opposite major surface of said TPU layer is coronatreated. In some embodiments, said pressure sensitive adhesive is tackyat room temperature.

Multilayer protective films made according to the present invention areuseful, for example, as paint protection films.

As used herein:

the term “polyisocyanate” refers to an organic isocyanate having atleast two isocyanate groups (for example, a diisocyanate, triisocyanate,etc.); and

the term “polyol” refers to an alcohol having at least two hydroxylgroups (for example, a diol, triol, etc.).

Other features and advantages of the present invention will be apparentfrom the following description of embodiments thereof, and from theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a cross-sectional view of one multilayer film prepared accordingto an exemplary method of the present invention;

FIG. 2 is a schematic depiction of an exemplary reactive coating processcorresponding to step (i) of the method of the present invention; and

FIG. 3 is a schematic depiction of an exemplary reactive extrusionprocess corresponding to step (ii) of the method of the presentinvention.

DETAILED DESCRIPTION

Although the present invention is herein described in terms of specificembodiments, it will be readily apparent to those skilled in this artthat various modifications, rearrangements, and substitutions may bemade without departing from the spirit of the invention.

A multilayer protective film, made according to the present invention,comprises a first or PU layer, a second or TPU layer and a PSA layer.The polyurethane comprises at least one of a polyester-basedpolyurethane or a polycarbonate-based polyurethane (for example, acombination of a polyester-based polyurethane or a polycarbonate-basedpolyurethane).

Referring now to FIG. 1, an exemplary multilayer film 10 made inaccordance with the principles of the present invention includes atleast a first or PU layer 12, a second or TPU layer 14 and a third orPSA layer 16. An optional releasable carrier web or liner 18 may bereleasably bonded so as to protect the surface of the PU layer 12. It istypically desirable for the film 10 to also include another releaseliner 20 releasably bonded so as to protect the PSA layer 16.

In some embodiments, the PU layer consists of, consists primarily of, orat least comprises a solvent-based or water-based polyurethane. Thewater-based polyurethane may be made from an aqueous-based polyurethanedispersion (that is, PUD). The solvent-based polyurethane may be madefrom a solvent-based polyurethane solution (that is, PUS). In somecases, it may be desirable to use PUDs, because of the elimination ofthe volatile solvents typically associated with using PUSs.

In some embodiments, the PU layer consists of, consists primarily of, orat least comprises a polyurethane layer formed directly bypolymerization of a layer comprising at least one polyisocyanate and atleast one polyol (that is, RPU). Such a layer may be formed, forexample, by either method (i) or method (ii) described hereinbelow. Insome cases, it may be desirable to use RPUs, because of the eliminationof the volatile solvents and the energy required to dry PUDs and PUSs.

The TPU layer consists of, consists primarily of, or at least comprisesa polycaprolactone-based TPU (that is, thermoplastic polyurethane).

The PSA layer comprises a pressure sensitive adhesive, and preferablyone that is tacky at room temperature. The PU layer is bonded to onemajor surface of the TPU layer and the PSA layer is bonded to anopposite major surface of the TPU layer such that the TPU layer issandwiched between the PU layer and the PSA layer.

Steps (i) and (ii) involve reaction of at least one polyol with at leastone polyol. Useful polyols include, for example, polyester polyols,polycarbonate polyols, and combinations thereof.

Examples of suitable polyols include materials commercially availableunder the trade designation DESMOPHEN from Bayer Corporation(Pittsburgh, Pa.). The polyols can be polyester polyols (for example,DESMOPHEN 631A, 650A, 651A, 670A, 680, 110, and 1150); polyether polyols(for example, DESMOPHEN 550U, 1600U, 1900U, and 1950U); or acrylicpolyols (for example, DESMOPHEN A160SN, A575, and A450BA/A);polycaprolactone polyols such as, for example, those caprolactonepolyols available under the trade designation TONE from Dow Chemical Co.(Midland Mich.) (for example, TONE 200, 201, 230, 2221, 2224, 301, 305,and 310) or under the trade designation CAPA from Solvay (Warrington,Cheshire, United Kingdom) (for example, CAPA 2043, 2054, 2100, 2121,2200, 2201, 2200A, 2200D, 2100A, 3031, 3091, and 3051)); polycarbonatepolyols (for example, those polycarbonate polyols available under thetrade designations PC-1122, PC-1167, and PC-1733 from Picassian Polymers(Boston, Mass.) or under the trade designation DESMOPHEN 2020E fromBayer Corp.); and combinations thereof. The choice of the degree ofreactive (for example, —OH) functionality (for example, difunctional)will generally be selected depending on the degree of crosslinkingdesired in the resultant polyurethane.

Examples of suitable polyisocyanates include: aromatic diisocyanates(for example, 2,6-toluene diisocyanate; 2,5-toluene diisocyanate;2,4-toluene diisocyanate; m-phenylene diisocyanate; p-phenylenediisocyanate; methylene bis(o-chlorophenyl diisocyanate);methylenediphenylene-4,4′-diisocyanate; polycarbodiimide-modifiedmethylenediphenylene diisocyanate;(4,4′-diisocyanato-3,3′,5,5′-tetraethyl) diphenylmethane;4,4′-diisocyanato-3,3′-dimethoxybiphenyl (o-dianisidine diisocyanate);5-chloro-2,4-toluene diisocyanate; and 1-chloromethyl-2,4-diisocyanatobenzene), aromatic-aliphatic diisocyanates (for example, m-xylylenediisocyanate and tetramethyl-m-xylylene diisocyanate); aliphaticdiisocyanates (for example, 1,4-diisocyanatobutane;1,6-diisocyanatohexane; 1,12-diisocyanatododecane; and2-methyl-1,5-diisocyanatopentane); cycloaliphatic diisocyanates (forexample, methylenedicyclohexylene-4,4′-diisocyanate;3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophoronediisocyanate); 2,2,4-trimethylhexyl diisocyanate; andcyclohexylene-1,4-diisocyanate), polymeric or oligomeric compounds (forexample, polyoxyalkylene, polyester, polybutadienyl, and the like)terminated by two isocyanate functional groups (for example, thediurethane of toluene-2,4-diisocyanate-terminated polypropylene oxideglycol); polyisocyanates commercially available under the tradedesignation MONDUR or DESMODUR (for example, DESMODUR XP7100 andDESMODUR 3300) from Bayer Corporation (Pittsburgh, Pa.); andcombinations thereof.

If cross-linking is desired (for example, in the case of a PU layer),one or more triisocyanates in combination with at least one diisocyanatein the reactive components used to make the PU layer, however this isnot a requirement.

If substantially no-crosslinking is desired (for example, in the case ofa TPU layer) the polyisocyanates and polyols are typically selected suchthat they are difunctional (that is, diisocyanate or diol), however aminor amount of cross-linking may be tolerable in some cases.

In general, the amount of polyisocyanate to polyol is selected inapproximately stoichiometrically equivalent amounts, although otherratios may be used (for example, having excess polyisocyanate or excesspolyol). Those skilled in the art will recognize that any excessisocyanate present after reaction with the polyol will typically reactwith materials having reactive hydrogens (for example, adventitiousmoisture, alcohols, amines, etc.).

A catalyst may be used to facilitate reaction between the polyol and thepolyisocyanate. Urethane catalysts are well known in the art andinclude, for example, tin catalysts (for example, dibutyltin dilaurate).

In at least some cases, it may be desirable to use at least some (forexample, use exclusively) aliphatic materials in construction thepresent multilayer film such as, for example, an aliphatic water-basedpolyurethane, an aliphatic polycaprolactone-based thermoplasticpolyurethane, or a combination thereof. For example, in making thepolyurethane, one or a combination of aliphatic polyols, aliphaticdiisocyanates, and aliphatic triisocyanates may be used.

In at least some cases, it may be desirable for the present multilayerfilm to use a polyurethane that is at least a slightly crosslinkedpolyurethane but not a thermoset polyurethane. As used herein, a“slightly crosslinked polyurethane” is one that may exhibit at leastenough melting, or at least enough softening, if heated to asufficiently high temperature, to form a bond that is strong enough topass the “Tape Snap Adhesion Test” if a layer of the polyurethane islaminated to a layer of the thermoplastic polyurethane. In contrast, asused herein, a “thermoset polyurethane” is one that is so heavilycrosslinked that it does not exhibit a sufficient amount of melting orsoftening if heated. That is, a thermoset polyurethane will generallyburn rather than melt or soften, and would not form a bond that isstrong enough to pass the “Tape Snap Adhesion Test” if a layer of thethermoset polyurethane is laminated to a layer of the thermoplasticpolyurethane, even if the thermoplastic polyurethane is heated before itis laminated.

The multilayer film may be easier to apply if the PSA layer consists of,consists primarily of, or at least comprises a pressure sensitiveadhesive that is tacky at room temperature (that is, around 75° F.(22-24° C.)).

For paint protection applications, the multilayer film is typicallytransparent or translucent. The multilayer film may be transparent,translucent, or even opaque for other surface protection or enhancementapplications, as desired. For some applications, it may be desirable forthe multilayer film to be colored. The multilayer film may be colored,for example, by including a pigment or other coloring agent in one ormore of its layers.

If used as a paint protection film, it is typically desirable for thepresent multilayer film to be sized and shaped to conform to the surfaceto be protected, before the film is applied. Pre-sized and shaped piecesof the present multilayer film may be commercially desirable forprotecting the painted surface of various body parts of a vehicle suchas, for example, an automobile, aircraft, watercraft, snowmobile, truck,or train car, especially those portions of the vehicle body (forexample, the leading edge of the front hood and other leading surfacesand/or rocker panels) that are exposed to such hazards as flying debris(for example, tar, sand, rocks, and/or insects).

Method of Making

A method of making a multilayer protective film, according to thepresent invention comprises: (a) forming a first or PU layer; (b)forming a second or TPU layer; (c) forming a PSA layer; (d) bonding onemajor surface of the PUD layer to one major surface of the TPU layer;and (e) bonding the PSA layer (for example, by corona treating andthermally laminating, coating or otherwise applying the pressuresensitive adhesive so as to adhere) to an opposite major surface of theTPU layer, with the TPU layer being sandwiched between the PU layer andthe PSA layer. At least one of steps (a) or (b) comprises step (i), step(b) comprises step (ii), or step (a) comprises step (i) and step (b)comprises step (ii).

The PU layer may consist of, consist primarily of, or at least comprisea polyurethane made from an aqueous-based polyurethane dispersion (thatis, PUD) or a polyurethane made from a solvent-based polyurethanesolution. The polyurethane may be a polyester-based polyurethane, apolycarbonate-based polyurethane or a combination of both. The TPU layerconsists of, consists primarily of or at least comprises apolycaprolactone-based TPU (that is, thermoplastic polyurethane). ThePSA layer comprises a pressure sensitive adhesive, and preferably onethat is at least somewhat tacky at room temperature.

In the practice of the method of the present invention, the PU layer maybe formed using conventional practices such as, for example, by theaqueous dispersion or solvent solution mixture being cast or otherwisecoated onto a releasable carrier web or liner. Those skilled in the artare capable of casting or otherwise coating the aqueous dispersion orsolvent solution mixture of the present invention onto a releasablecarrier web using known techniques. Suitable carriers may include filmssuch as biaxially oriented polyester and papers that may be coated orprinted with a composition that will enable release from thepolyurethane compositions. Such coatings include those formed frompolyacrylics, silicone, and fluorochemicals. The aqueous dispersion orsolvent solution mixture may be coated onto a carrier web usingconventional equipment known by those skilled in the art such as knifecoater, roll coaters, reverse roll coaters, notched bar coaters, curtaincoaters, roto-gravure coaters, rotary printer and the like. Theviscosity of the aqueous or solvent mixture may be adjusted to the typeof coater used. The water or solvent in the coated mixture is thenremoved such as, for example, by drying.

The PU layer may be formed, for example, by casting or otherwise coatingan aqueous PUD (that is, polyurethane dispersion) or solvent PUS (thatis, polyurethane solution) onto a readily releasable carrier web orliner (for example, a polyester carrier web) having a smooth surface. Byusing such a carrier web or liner having a smooth surface on which toapply the aqueous PUD or solvent PUS, the resulting PU layer may exhibitan exposed major surface with the appearance of having been cast onto asmooth major surface of a releasable carrier web or liner, dried orotherwise cured and the carrier web removed. In contrast, if the PUlayer is open air dried or cured such as, for example, by casting orcoating the PU layer onto the one major surface of the TPU layer, thenthe exposed major surface of the PU layer would not exhibit the samesmooth appearance.

The TPU layer may be formed by extruding the polycaprolactone-based TPU(that is, thermoplastic polyurethane) at an elevated temperature throughan extrusion die. The TPU layer may also be formed by casting orotherwise molding (for example, injection molding) thepolycaprolactone-based TPU into the shape desired.

The PU and TPU layers may be bonded together, for example by laminatingthe layers at an elevated temperature and pressure. For example, onemajor surface of the PU layer may be cold laminated under pressure toone major surface of the extruded TPU layer, while at least the onemajor surface of the TPU layer is, or both the TPU layer and the PUlayer are, at an elevated temperature that is sufficiently high enoughto facilitate adequate bonding between the PU layer and the TPU layer.As used herein, “cold laminating” refers to the layers being laminatedtogether between two nip surfaces in about a room or ambient temperatureenvironment (that is, the layers are not kept in an intentionally heatedenvironment during the laminating process). The nip surfaces may be twonip rollers, a stationary nip surface (for example, a low frictionsurface of a flat or curved plate) and a nip roller, or two stationarynip surfaces. The laminating process may even be performed in a belowambient temperature environment (that is, the layers are intentionallycooled during the laminating process). For example, one or both of thenip surfaces may be chilled to a temperature below ambient, in order tocool the exposed major surfaces of the polyurethane layers (that is, themajor surfaces the nip surfaces contact). The use of such chilledsurfaces may eliminate, or at least help reduce, warping of the layersresulting from the laminating process. At the same time, the majorsurfaces that make contact at the interface between the polyurethanelayers remain at the elevated temperature long enough to be sufficientlybonded together by the laminating pressure exerted by the nip surfaces.Such cold laminating may be accomplished by laminating the newlyextruded TPU layer directly onto a preformed PU layer, while the TPUmaterial still retains significant heat from the extrusion process. ThePU layer is typically still releasably bonded to the carrier web orliner, to provide additional structural strength.

Alternatively, one major surface of the PU layer may also be bonded toone major surface of the extruded TPU layer by using a hot laminatingprocess. With this process, the initial temperature of both the PU layerand the TPU layer is about room temperature or at least a temperaturethat is too low to facilitate adequate bonding between the PU layer andthe TPU layer. Then, at least the one major surface of the TPU layer, atleast the one major surface of the PU layer, or the one major surfacesof both the PU layer and the TPU layer are heated to an elevatedtemperature that is sufficiently higher than room temperature tofacilitate adequate bonding between the PU layer and the TPU layer underthe laminating pressure. With the hot laminating process, the layers areheated before or during the application of the laminating pressure. If ahot laminating process is used, a major surface of the TPU layer istypically releasably laminated to a readily releasable carrier web orliner (for example, a polyester carrier web) directly after the TPUlayer is extruded, in order to provide the freshly extruded TPU layerwith additional structural support.

Acceptable minimum temperatures and pressures for bonding the layerstogether, using either the cold or hot laminating process, have includeda temperature of at least about 200° F. (93° C.) and a pressure of atleast about 15 lb/in² or psi (10.3 N/cm²).

To facilitate or at least improve bonding between the TPU layer and thePSA layer it may be desirable to corona treat (for example, air or N₂corona treatment) and thermally laminate the major surface of theextruded TPU layer to be bonded to the PSA layer. To accomplish this,the major surface of the TPU layer, which is not in contact with the PUlayer, is exposed and then corona treated. If a hot laminating processis used (that is, the TPU layer is extruded onto a releasable carrierweb or liner), the carrier web or liner must first be stripped off ofthe TPU layer.

As discussed above, at least one of steps (a) or (b) comprises step (i),step (b) comprises step (ii), or step (a) comprises step (i) and step(b) comprises step (ii).

Step (i) comprises forming a rolling bank of a polyurethane precursormaterial comprising at least one polyisocyanate and at least one polyol,wherein the rolling bank contacts first and second substrates; passingthe first and second substrates with the polyurethane precursor materialdisposed therebetween through a nip; heating the polyurethane precursormaterial under conditions such that it forms the PU layer in contactwith the first and second substrates; and optionally removing at leastone of the first or second substrates from the PU layer to expose anouter surface of the PU layer.

An exemplary process 200 for step (i) is shown in FIG. 2. Referring nowto FIG. 2, reactive component(s) 203 is/are fed into static mixer 210.The mixed component(s) are then fed to form rolling bank 215 which isdisposed ahead of and between first and second substrates 221, 222 whichare unwound from feed rolls 223, 224. As first and second substrates221, 222 advance through nip 230 formed by first platen 240 and notchbar 235 entrapped air bubbles 217 are substantially or completelyremoved to give layer 250 which, after passing optional insulationbarrier 260, contacts optional heated platen 265 which facilitatespolymerization of the reactive component(s), if desired, to form a layer270 disposed between first and second substrates 221, 222. In thisregard, it will be recognized that although a heated platen is shown inFIG. 2, any heating means may be used including, for example, infraredlamps, ovens, microwave radiation, and heated platens. Layer 270 maycorrespond to the PU layer or the TPU layer depending on the degree ofcross-linking (for example, due to the inclusion of polyisocyanateshaving an average functionality of greater than two).

In some embodiments, (for example, those wherein at least the firstsubstrate is a release liner) first substrate 221 is then removed toexpose a surface of layer 270 to which additional layers may belaminated, or on which subsequent layers may be provided.

Advantageously, by using the above-described coating process it isgenerally possible to produce coated layers of material that aresubstantially void-free (that is, free of bubbles or pinhole coatingdefects that are readily visible to an unaided human eye) overrelatively large areas (for example, greater than 1 square meter).

In general, the effectiveness of entrapped air removal will vary withthe materials and conditions used, but typically a gap of 20 mils (0.51mm) or less (for example, less than or equal to 15 mils (0.38 mm), 10mils (0.25 mm), 8 mils (0.20 mm), or even less than or equal to 5 mils(0.17)) may be effective. The gap may be created by any suitable meansincluding, for example, nip roll(s), bars, platen(s), knife edge(s), ora combination thereof. Multiple nips (for example, of decreasing gap)may also be used.

The reactive components (for example, polyol and polyisocyanate) shouldtypically be fed at a sufficient rate such that the rolling bank is notdepleted.

In general, the first and second release substrates should have the samerate of travel, however this is not a requirement. In some embodiments,the first substrate and or/second may be in the form of a continuousbelt. In some embodiments, the first and second substrates may comprise,for example, a mold or a release liner.

Examples of suitable release liners include: paper, polymer film (forexample, polyester, polyethylene, or polypropylene), or other polymericfilm material. The release liner may be coated with a material todecrease the amount of adhesion between the release liner and theadhesive layer. Such coatings can include, for example, a silicone orfluorochemical material. Any commercially available release liner may beused in the present invention.

The first and/or second substrate may comprise a release liner, the PUlayer, the TPU layer, the PSA layer, or a combination thereof, asdesired. For example, in one exemplary embodiment, second substrate 222may comprise a release liner having a TPU layer thereon, wherein step(i) provides a PU layer on the TPU layer. In another exemplaryembodiment, second substrate 222 may comprise a release liner having aPSA layer thereon, wherein step (i) provides a TPU layer on the PSAlayer. In yet another exemplary embodiment, second substrate 222 maycomprise a release liner having a PSA thereon and a TPU layer on the PSAlayer opposite the release liner.

If using method (i) to prepare the PU layer, at least one polyisocyanateand/or at least one polyol should typically have an average reactivefunctionality (for example, —NCO or —OH functionality) of greater thantwo, although this is not a requirement (for example, if a minor amountof trifunctional amine or aminoalcohol is included with the polyol).

If using method (i) to prepare the TPU layer, the polyisocyanates andpolyols should typically have an average reactive functionality (forexample, —NCO or —OH functionality) of two or less, although this is nota requirement (for example, if a minor amount of crosslinking isacceptable).

Step (ii) comprises introducing components comprising a diisocyanate anda diol into an extruder to provide a molten thermoplastic polyurethane;extruding the molten thermoplastic polyurethane through a die onto athird substrate; passing at least the third substrate and the extrudedmolten thermoplastic polyurethane through a nip to provide a layer ofthermoplastic polyurethane on a substrate; and solidifying thethermoplastic polyurethane. Solidification of the extruded moltenpolyurethane may occur contemporaneously with, or subsequent to, formingthe polyurethane layer.

Typically, the polyisocyanate(s) and polyol(s) are introducedsimultaneously into the bore of the extruder, however, they may beintroduced sequentially. As the polyisocyanate(s) and polyol(s) movethrough the extruder, typically with heating, they react with oneanother to form a thermoplastic polyurethane (TPU), which is extrudedthrough a melt die to form the TPU layer. In some cases, additionalpolymerization may occur after extrusion. The thermoplastic polyurethaneis extruded from melt die 330 onto a substrate to form the TPU layer.Referring now to FIG. 3, which shows an exemplary process 300 for step(ii), molten thermoplastic polyurethane 303 is extruded onto substrate305 at nip 310, which is formed by rolls 320, 322.

In general, the melt die is maintained at a temperature above themelting point of the polymer (for example, at least 20° C. above themelting point).

The substrate may comprise a release liner, the PU layer, the PSA layer,or a combination thereof, as desired. For example, in one exemplaryembodiment, substrate 305 may comprise a release liner having a PU layerthereon, wherein step (ii) provides a TPU layer on the PU layer. Inanother exemplary embodiment, substrate 305 may comprise a release linerhaving a PSA layer thereon, wherein step (ii) provides a TPU layer onthe PSA layer.

If the raw materials used in either steps (i) or (ii) are solids orsemi-solids, they may be heated to a fluid state before handling (forexample, mixing or pumping) them.

Further details concerning multilayer polyurethane films and methods formaking and using them may be found, for example, in PCT Pat. Appln.US2006/015699 (Ho et al), filed Apr. 26, 2006, the disclosure of whichis hereby incorporated herein by reference in its entirety.

EXAMPLES Test Methods Tape Snap Adhesion Test

This test provides an indication of how well a film construction remainstogether after exposure to various conditions. Sample of thepressure-sensitive adhesive coated polyurethane construction are adheredto painted panels and aged for 24 hours at room temperature. Separatepanels are aged using each of the test conditions listed below:

-   -   Water Immersion (10 D—WI): panel immersed in 40° C. water bath        for 10 days;    -   Fog chamber (7D—100/100): panel aged on a rack at about 30        degree angle and exposed for 7 days at 38° C. in a chamber with        100% relative humidity;    -   Salt spray (7D—SS): panel placed on a rack at about 60 degree        angle and exposed for 7 days at 35° C. using a 5 percent by        weight sodium chloride solution in a salt fog chamber; and    -   Heat aging (7D—80C): panel placed on a rack for 7 days in an        oven set at 80° C. oven.

After aging, the test panel is dried if needed, and then conditioned atroom temperature (about 22° C.) for 24 hours. The construction is thencross-hatched with a razor blade to form a grid of about 20 squares eachmeasuring about 1 mm by 1 mm. A strip of 610 Tape (available from 3MCompany (St. Paul, Minn.)) is adhered over the cross-hatched area usingfirm finger pressure, and then the tape is snapped off with a quickpull. The sample is rated as Pass (no delamination of any squares thefilm or blistering of the film is observed after tape is removed) orFail (at least one square is removed with the tape or blistering isobserved after drying).

The color change in the films before and after aging is also measured.The film color change is measured according to the standard proceduredetailed in ASTM D2244-05 “Standard Practice for Calculation of ColorTolerances and Color Differences from Instrumentally Measured ColorCoordinates” using a CHROMA SENSOR CS-5 instrument from Data ColorInternational (Lawrenceville, N.J.). Delta E (ΔE) represents the totalcolor change in the film before and after aging in differentenvironments. Delta YI ((ΔYI) represents the yellowness index changebefore and after filmed aged in different environments.

Gravel Test

The gravel test is conducted according to ASTM D3170-03 “Standard TestMethod for Chipping Resistance of Coatings”. A 4-inch by 4-inch squarefilm sample is applied to a clear coated steel panel coated with a whiteclearcoat/basecoat paint system. The panel with film is then conditionedat −30° C. for at least 3 hours. The panel is mounted vertically andexposed to the impact force of 780 grams of gravel at a pressure of 60psi (0.4 MPa). The panel with film is then aged for 7 days in salt sprayenvironment for corrosion test.

Materials Used In the Examples

ABBREVIATION DESCRIPTION U933 water-based, polycarbonate-basedpolyurethane dispersion available under the trade designation U933 fromAlberdingk Boley, Inc. (Charlotte, NC) AMP-95 aminomethylpropanol pHadjuster available under the trade designation AMP-95 from AngusChemical Co. (Buffalo Grove, IL) DABCO T-12 dibutyltin dilaurateavailable under the trade designation DABCO T-12 from Air Products andChemicals, Inc. (Allentown, PA) DESMODUR N3300 aliphatic isocyanateavailable under the trade designation DESMODUR N3300 from Bayer, Inc.,Material Science, LLC (Pittsburgh, PA ) DESMODUR W dicyclohexylmethanediisocyanate available under the trade designation DESMODUR W from BayerMaterialScience LLC (Pittsburgh, PA) K-FLEX 188 polyester polyolavailable under the trade designation K- FLEX 188 from King Industries,Inc. (Norwalk, CT) NEOCRYL CX100 aziridine crosslinker available underthe trade designation NEOCRYL CX100 from DSM (Waalwijk, The Netherlands)POLY BD R20LM low molecular weight hydroxy terminated polybutadieneavailable under the trade designation POLY BD R20LM from Sartomer Co.(Exton, PA) TECOFLEX CLA thermoplastic caprolactone-based polyurethaneavailable 93A-V under the trade designation TECOFLEX CLA 93A-V fromNoveon, Inc. (Cleveland OH) TINUVIN 123 hindered amine light stabilizerbased on aminoether functionality available under the trade designationTINUVIN 123 from Ciba Specialty Chemicals Corp. (Tarrytown, NY) TINUVIN292 liquid hindered amine light stabilizer available under the tradedesignation TINUVIN 292 from Ciba Specialty Chemicals Corp. TINUVIN 1130hydroxyphenylbenzotriazole type UV absorber available under the tradedesignation TINUVIN 1130 from Ciba Specialty Chemicals Corp. TONE 2221linear polycaprolactone polyol having a number average molecular weightof 2000, a functionality of 2, hydroxyl number (mg KOH/g) of 56.1, and ahydroxyl equivalent weight of 1000 g/eq, available under the tradedesignation TONE 2221 from Dow Chemical Co. (Midland MI) TONE 2241linear polycaprolactone polyol having a number average molecular weightof 1000, a functionality of 2, hydroxyl number (mg KOH/g) of 112.2, anda hydroxyl equivalent weight of 500 g/eq, available under the tradedesignation TONE 2241 from Dow Chemical Co. TRITON GR-7M sulfosuccinatetype anionic surfactant available under the trade designation TRITONGR-7M from Dow Chemical Co. TYZOR DC bis(ethylacetoacetato)diisopropoxytitanium available under the trade designationTYZOR DC from E. I. du Pont de Nemours & Co. (Wilmington, DE)

1,4-Butanediol is commercially available, for example, fromInternational Specialty Products (Wayne, N.J.). Butyl carbitol iscommercially available, for example, from Eastman Chemical Co.(Kingsport, Tenn.). 2-Ethylhexyl 2-cyano-3,3-diphenylacrylate, a UVlight absorber, is commercially available, for example, from AldrichChemical Co. (Milwaukee, Wis.).

Example 1

A polyurethane film was prepared by reactively extruding a two partpolyurethane composition through a 25-mm co-rotating twin screw extruder(Berstorff model ZE25 twin screw extruder available from Berstorff USA(Florence, Ky.)). The extruder had 10 barrel zones that wereindependently heated. A melt pump was used at the output end of the twinscrew extruder to feed the melt into a 25.4-cm (10-inch) wide coathanger die (available from Extrusion Dies, Inc. (Chippewa Falls, Wis.).The die had a 1.27-mm (0.050-inch) die opening with an adjustable lip.The extrusion process conditions are reported in Table 1 (below).

TABLE 1 Process Condition Setting Extruder RPM (rpm) 75 Extruder Amps(amps) 10 Zone 2 (° C.) 160 Zone 3 (° C.) 165 Zone 4 (° C.) 170 Zone 5(° C.) 170 Zone 6 (° C.) 180 Zone 7 (° C.) 180 Zone 8 (° C.) 180 Zone 9(° C.) 180 Zone 10 (° C.) 180 Die Zone (° C.) 185 Melt Temp (° C.) 97Neck Tube (° C.) 185 Block Heater (° C.) 185 Chill Roll (° C.) 16 MeltPump RPM (rpm) 21 Melt Pump pressure in (psi) 30 Melt Pump pressure out(psi) 470

Part A (polyol mixture) and Part B (isocyanate) of the compositionsreported in Table 2 (below) were simultaneously fed into zone 2. Part Awas heated to about 55° C. in an electrically heated vessel and fed intothe extruder with a gear pump (available from Zenith Pumps, Monroe,N.C.) at a flow rate of 67.83 grams/minute, and Part B was fed into theextruder using piston pump (Gilson 100SC HPLC piston pump available fromGilson Inc, Middleton, Wis.) at a flow rate of 45.68 grams/minute.

TABLE 2 PART A POLYOL FORMULATIONS Example 1 Example 2 TONE 2221 polyol3703.7 1240.6 TONE 2241 polyol 0 2394.9 1,4-butanediol 704.4 772.62-ethylhexyl 2-cyano- 45.4 45.4 3,3-diphenylacrylate Tinuvin-292 45.445.4 10 weight percent 45.4 45.4 DABCO T-12 in TONE 2221

The extrudate from the die was cast as a film having nominal thicknessof 0.15 mm (6 mils) onto a clear coat film disposed on a release coatedpolyester carrier web moving at a winder speed of about 1.5 meters/min(5 ft/min).

The clear coat film was prepared from an aqueous polyurethane coatingdispersion by mixing 83.78 grams of U933 dispersion and an antioxidantdispersion. The dispersion was prepared by mixing 0.03 grams of AMP-95,0.19 grams Triton GR-7M, 8.47 grams of butyl carbitol, 1.08 grams of2-ethylhexyl 2-cyano-3,3-diphenylacrylate, and 0.45 grams TINUVIN 123and diluting with de-ionized water to maintain the viscosity between 70cps (70 mPa-sec) and 180 cps (180 mPa-sec). Just prior to coating, 1.30percent by weight of a crosslinker (50 percent by weight solidsNEOCRYL-100 in deionized water) were added under agitation. Thedispersion was coated to a thickness of about 50 micrometers onto anuntreated polyester carrier web. The coated dispersion was dried andcured sequentially in separate ovens for about 0.5 minutes each. Theoven temperatures were set at 121° C., 149° C., and 163° C. for thefirst, second, and third ovens, respectively. The resulting clear filmwas about 11-12 microns thick.

After the laminate was cooled, the exposed side of the extrudedpolyurethane film was corona treated at 2 kilowatts and thermallylaminated to an acrylic pressure-sensitive adhesive on a paper releaseliner using a hot can set at 121° C. (250° F.) to form a polyurethaneconstruction. The polyester carrier was removed and the polyurethaneconstruction was tested for environmental aging followed by tape snapadhesion test, and gravel tests. The results are summarized in Table 3.

Comparative Example C1

Comparative Example C1 was multilayer film prepared according to Example1 of PCT Pat. Appln. No. US2006/015699 (Ho et al), filed Apr. 26, 2005.

TABLE 3 Comparative Example 1 Example C1 Test Adhesion AdhesionCondition Pass/Fail Δ E ΔYI Pass/Fail Δ E ΔYI TAPE SNAP ADHESION TEST 10D-WI Pass 0.26 0.46 Pass 0.28 0.5 7D100/100 Pass 0.18 0.16 Pass 0.15−0.08 7D-SS Pass 0.21 −0.63 Pass 0.17 −0.05 7 D-80C Pass 0.72 1.12 Pass0.62 1.05 GRAVEL TEST Pass No Rust or Pass No Rust or Puncture Puncture

Example 2

A polyurethane film was prepared according to the procedure outlined inExample 1, except that the Composition for Example 2 was used, and PartA was fed into the extruder at a flow rate of 68.70 grams/minute andPart B was fed into the extruder at a flow rate of 44.70 grams/minute.The extrudate was cast at a thickness of 0.15 mm (6 mil) onto a clearcoat film disposed on a polyester carrier to form a polyurethaneconstruction. The clear coated liner used was prepared according to theprocedure of Example 1 of U.S. Pat. No. 6,607,831 (Ho et al.).

Example 3

A 2-part polyurethane composition was prepared by mixing 6 grams ofDESMODUR N3300 with 7.6 grams K-FLEX 188 polyol and 2 drops ofdibutyltin dilaurate. All amounts were in parts by weight. Twosubstrates were positioned between a slotted knife and a platen with agap of about 0.15 mm (6 mils) between the two substrates. Thecomposition is fed between the substrates to form a rolling bank just infront of the slotted knife. The substrates were pulled downweb throughthe knife and a film coating was formed between them. The coatingthickness was approximately 127 micrometers (5 mils). The bottomsubstrate was a 0.30 mm (12 mil) thick sheet of thermoplasticpolyurethane made from TECOFLEX CLA 93A-V. The bottom substrate was alsocoated with a pressure sensitive adhesive which was protected by asilicone coated release liner. The top substrate was a silicone releasecoated polyester film. The coating was allowed to polymerize at roomtemperature on a flat surface over the course of several days to form apolyurethane construction suitable for a paint protection film.

Examples 4-9

A clear coat dispersion was prepared by mixing 92.35 parts of U933, 4.44parts of a polyaziridine solution (50 parts of NEOCRYL CX100 in 50 partsdeionized water), and 3.21 parts of an antioxidant emulsion (1.62 partsof water, 0.49 part TINUVIN 292, 0.83 part TINUVIN 1130, 0.18 partsTRITON GR-7M, 0.09 part of AMP-95. The dispersion was coated onto asmooth silicone coated 50.8 micrometers (2 mils) thick polyester filmusing a notched bar coater with a gap setting of 152.4 μm (6 mils)between the film and the bar coater. The coater speed was set at 1.52mpm (5 feet/minute) and the film was dried and cured in a 3-zone ovenwith oven temperatures set at 79.4° C./140.6° C./198.9° C. (175° F./285°F./390° F.) to form a polyurethane film having a thickness of about 25.4micrometers (1 mil). Each oven zone was about 3.66 m (12 feet) long. Theresultant film (Film A) had a cross-linked polyurethane PU layer on arelease liner.

Two-part polyurethane compositions having the formulations reported inTable 4 were prepared by mixing the reactive components K-FLEX 188, POLYBD R20LM, DESMODUR W, and a tin catalyst. The compositions were thencoated at a thickness of about 5 mils (130 micrometers) according to theprocedure of Example 3, except that the bottom substrate was a siliconerelease coated polyester film. The coating was allowed to polymerize atroom temperature on a flat surface over the course of several days toform a polyurethane protective layer. The top silicone release coatedpolyester film was then removed from the polyurethane surface. Theresultant films (Films B4-B9) had a thermoplastic polyurethane TPU layeron a release liner.

TABLE 4 THERMOPLASTIC FILM COMPOSITION POLYBD dibutyltin DESMODUR W,K-FLEX R20LM, dilaurate Example Grams 188, grams grams) (drops) 4 3 0.5613.4 3 5 3 1.12 11.91 3 6 3 1.68 10.42 3 7 3 2.24 8.93 3 8 3 2.79 7.44 39 3 2.19 3.72 3

While not physically performed, it is believed that the PU layer of FilmA could be successfully laminated to the TPU layer of any of FilmsB4-B9, and a pressure-sensitive adhesive PSA layer added to thelaminate, to form a multilayer polyurethane protective film suitable foruse, for example, as a paint protection film

Example 10

A TPU layer between two silicone release coated polyester films wasprepared as in Example 4, except using as the reactive components: 10grams of POLYBD R20LM, 2 grams of DESMODUR W, 2 drops of TYZOR DC. Theresultant construction was allowed to cure to completion over the courseof several months, after which the TPU layer was tacky to the touch. Oneof the release liners was then removed from the TPU layer, which wasthen laminated to the PU layer of Film A from Example 4. The opposingrelease liner on the TPU layer was then removed, and an acrylic psalayer on a microstructured release liner was laminated to the surface ofthe TPU layer without any pretreatment. The liner from Film A was thenremoved, and a one inch wide sample of the resulting multilayerpolyurethane protective film was cut into a length of 3 inches. Themicrostructured release liner was then removed from the psa layer, andthe resultant construction was laminated to a painted metal panel.

From the above disclosure of the general principles of the presentinvention and the preceding detailed description, those skilled in thisart will readily comprehend the various modifications, re-arrangementsand substitutions to which the present invention is susceptible.Therefore, the scope of the invention should be limited only by thefollowing claims and equivalents thereof.

We claim:
 1. A method of making a multi layer protective film, themethod comprising steps: (a) forming a PU layer comprising an at leastpartially crosslinked polyurethane, the at least partially crosslinkedpolyurethane comprising at least one of a polyester-based polyurethaneor a polycarbonate-based polyurethane; (b) forming a TPU layercomprising a polycaprolactone-based thermoplastic polyurethane; (c)forming a PSA layer comprising a pressure sensitive adhesive; (d)bonding one major surface of the PU layer to one major surface of theTPU layer; and (e) bonding the PSA layer to an opposite major surface ofthe TPU layer; wherein the TPU layer is sandwiched between the PU layerand the PSA layer, and wherein at least one of steps (a) or (b)comprises step: (i) forming a rolling bank of a polyurethane precursormaterial comprising at least one polyisocyanate and at least one polyol,wherein the rolling bank contacts first and second substrates; passingthe first and second substrates with the polyurethane precursor materialdisposed therebetween through a nip; heating the polyurethane precursormaterial under conditions such that it forms the PU layer or the TPUlayer in contact with the first and second substrates; and optionallyremoving at least one of the first or second substrates from the PUlayer or the TPU layer to expose an outer surface of the PU layer or theTPU layer, respectively; or step (b) comprises step: (ii) introducingcomponents comprising a diisocyanate and a diol into an extruder toprovide a molten thermoplastic polyurethane; extruding the moltenthermoplastic polyurethane through a die onto a third substrate; passingat least the third substrate and the extruded molten thermoplasticpolyurethane through a nip to provide a layer of thermoplasticpolyurethane on the third substrate; and solidifying the thermoplasticpolyurethane; or step (a) comprises step (i) and step (b) comprises step(ii).
 2. The method of claim 1, wherein steps (a) to (e) are carried outsequentially.
 3. The method of claim 1, wherein steps (a) to (e) arecarried out consecutively.
 4. The method of claim 1, wherein step (a)further comprises: coating an aqueous-based polyurethane dispersion ontoa releasable carrier.
 5. The method of claim 1, wherein step (a) furthercomprises: coating a solvent-based polyurethane solution onto areleasable carrier.
 6. The method of claim 1, wherein step (b)comprises: extruding, the polycaprolactone-based thermoplasticpolyurethane at an elevated temperature through a die to form the TPUlayer.
 7. The method of claim 6, wherein at least one of steps (a) or(b) comprises step (i).
 8. The method of claim 6, wherein step (b)comprises step (ii).
 9. The method of claim 6, wherein step (d)comprises: laminating the one major surface of the PU layer to the onemajor surface of the TPU layer while the one major surface of the TPUlayer is at an elevated temperature that is sufficiently higher thanroom temperature to facilitate adequate bonding between the PU layer andthe TPU layer.
 10. The method of claim 6, wherein step (d) comprises:laminating one major surface of the PU layer to one major surface of theTPU layer after said extruding and with at least the one major surfaceof the PU layer and the TPU layer being at a temperature that is too lowto facilitate adequate bonding between the PU layer and the TPU layer;and heating the one major surface of the TPU layer to an elevatedtemperature that is sufficiently higher than room temperature tofacilitate adequate bonding between the PU layer and the TPU layerduring said laminating, wherein said heating occurs before or duringsaid laminating.
 11. The method of claim 1, further comprising: coronatreating the opposite major surface of the TPU layer.
 12. The method ofclaim 11, further comprising: releasably laminating an opposite majorsurface of the TPU layer to a releasable carrier web after saidextruding.
 13. The method of claim 12, further comprising: exposing theopposite major surface of the TPU layer, after said releasablylaminating; and corona treating the opposite major surface of the TPUlayer, after said exposing and before said bonding the PSA layer. 14.The method of claim 1, wherein said at least partially crosslinkedpolyurethane is the reaction product of a polyol and at least adiisocyanate, and said polyol is a polyester polyol, a polycarbonatepolyol or a combination of both.
 15. The method of claim 14, whereinsaid polyol is an aliphatic polyol.
 16. The method of claim 1, whereinsaid at least one polyisocyanate comprises a diisocyanate and atriisocyanate.
 17. The method of claim 16, wherein said triisocyanate isan aliphatic triisocyanate.
 18. The method of claim 17, wherein saiddiisocyanate is an aliphatic diisocyanate.
 19. The method of claim 18,wherein said diisocyanate comprises isophorone diisocyanate.
 20. Themethod of claim 18, wherein said diisocyanate comprisesbis(4-isocyanatocyclohexyl)methane.
 21. The method of claim 18, whereinsaid at least partially crosslinked polyurethane is saidpolycarbonate-based polyurethane.
 22. The method of claim 18, whereinsaid at least partially crosslinked polyurethane is said polyester-basedpolyurethane.
 23. The method of claim 1, wherein said at least partiallycrosslinked polyurethane is a combination of said polyester-basedpolyurethane and said polycarbonate-based polyurethane.
 24. The methodof claim 23, wherein said polyurethane is an aliphatic polyurethane. 25.The method of claim 1, wherein said at least partially crosslinkedpolyurethane is a slightly crosslinked polyurethane.
 26. The method ofclaim 1, wherein said at least partially crosslinked polyurethane is awater-based polyurethane.
 27. The method of claim 1, wherein said atleast partially crosslinked polyurethane is a solvent-basedpolyurethane.
 28. The method of claim 1, wherein said PU layer has anexposed major surface with the appearance of having been cast onto asmooth major surface of a releasable carrier web, dried and the carrierweb removed.
 29. The method of claim 1, wherein the opposite majorsurface of said TPU layer is corona treated.
 30. The method of claim 1,wherein said pressure sensitive adhesive is tacky at room temperature.31. The method of claim 1, wherein said multilayer protective film istransparent.
 32. The method of claim 1, wherein said multilayerprotective film is colored.